If you're looking for one number that explains why the Phillies have struggled to break through in the first half of this season, here's my nominee. The team has hit 77 home runs thus far... and surrendered 104. Of their NL East rivals, the Braves have smacked 83 (about half by Andruw Jones) and given up 64; the Marlins are 59/46; the Mets are 79/65; and Washington is the only team joining the Phils with a negative HR balance--at 58 for, 59 against.
These numbers are easily enough explained--the ballpark, the flyball tendencies of the pitching staff, etc. And if anything, we might expect the cost of having surrendered nearly a third more homers than they've hit to be higher than it's been thus far. That it hasn't been is probably more a tribute to the lineup's on-base skills, and to the pitching staff's stinginess in doling out walks, than anything else: the Phils have drawn 292 bases on balls and given up 229. So when the big flies (or any other hits) come, we're somewhat more likely to have men on base than the opposition.
Still, it's hard to see the team playing deep into October unless this home run deficit is closed up.